The Journal of Korean Academy of Prosthodontics (대한치과보철학회지)
- Volume 38 Issue 5
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- Pages.575-582
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- 2000
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- 0301-2875(pISSN)
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- 2005-3789(eISSN)
FLEXURE STRENGTH AND MICROSTRUCTURE OF IPS EMPRESS 2 GLASS-CERAMIC ON HEAT-PRESSING AND HEAT TREATMENTS
열가압 및 열처리에 따른 IPS Empress 2 세라믹의 굴곡강도와 미세구조
- Oh, Sang-Chun (Department of Prosthodontics, School of Dentistry, Wonkwang University) ;
- Dong, Jin-Keun (Department of Prosthodontics, School of Dentistry, Wonkwang University) ;
- Luthy, Heinz (Clinic of Fixed and Removable Prosthodontics and Dental Materials Science, Center of Dental and Oral Medicine, University of Zurich) ;
- Scharer, Peter (Clinic of Fixed and Removable Prosthodontics and Dental Materials Science, Center of Dental and Oral Medicine, University of Zurich)
- Published : 2000.10.01
Abstract
This investigation was designed to determine whether heat-pressing and/or simulated heat treatments affected the flexure strength and the microstructure of the lithium disilicate glass-ceramic in the IPS Empress 2 system. Four groups of the specimens were prepared as follows: group 1 - as-received material, group 2 - heat-pressed material; group 3 - heat-pressed and simulated initial heat-treated material; group 4 - heat-pressed and the simulated heat-treated material with full firings for a final restoration. The three-point bending test and the scanning elec-tron microscope (SEM) analysis was conducted for the purpose of this study. The flexure strength of group 2 was significantly higher than that of group 1. However, there were no significant differences in strength among group 2, 3, and 4, and between group 1 and 4. The SEM micrographs of the lithium disilicate glass-ceramic showed the closely packed, multi-directionally interlocking microstructure of numerous lithium disilicate crystals protruding from the glass matrix. The crystals of the heat-pressed materials (group 2, 3, and 4) were a little denser and about two times bigger than those of the as-received material (group 1). This change of microstructure is more obviously exhibited particularly between group 1 and 2. However, there was no a marked difference among group 2, 3, and 4 after the heat-pressing procedure. Although there were significant increase of the strength and some changes of the microstructure after the heat-pressing operation, the combination of the heat-pressing and the simulated subsequent heat treatments did not produce the increase of strength of IPS Empress 2 glass-ceramic.
Keywords
- IPS Empress 2 system;
- Lithium disilicate glass-ceramic;
- Heat-pressing procedure;
- Simulated subsequent heat treatments;
- Flexure strength;
- Microstructure